Coronary heart disease is the most common single cause of death in the western world, representing about 20% of all deaths. This is equivalent to about 2 million deaths in Europe per year or four people per minute. In the US, over 8 million people exhibit acute (chest pain) symptoms in the Emergency Department (ED) of hospitals, with 1.5 million individuals having confirmed acute coronary symptom (ACS) events, accounting for 500,000 short term deaths. In patients presenting to the emergency room with chest pain, fewer than 15% are ultimately diagnosed as having ischemia or acute myocardial infarction (MI). Currently, blood tests for the cardiac specific isoform of troponin I or troponin T (TnI or TnT, respectively) are generally used for the diagnosis of acute myocardial infarction (due to cardiac muscle (cell) death). Creatine kinase (CK) MB and myoglobin can also be used, but are considered to be less specific for cardiac injury. However, although these cardiac biomarkers can identify patients with even small amounts of myocardial necrosis, there is an earlier time point in which the heart is in ischemia but is not yet in necrosis, and the diagnosis of cardiac ischemia in the absence of necrosis cannot currently be made with accuracy.
It would be useful to be able to identify subjects in this diagnostic window (having non-necrotic ischemia). Such a diagnostic tool would be of great value for triage in the emergency department. For example, it would allow earlier intervention, including earlier perfusion, to allow increased salvage of the injured myocardium; and it would prevent unnecessary admittance to the hospital of patients with non-cardiac chest pain. Furthermore, such an assay could delay therapy in subjects who do not exhibit diagnostic electrocardiographic (ECG) changes, and could help to improve the accuracy of current provocative tests for ischemia, such as exercise stress testing. The sooner intervention can be carried out, the less cardiac damage will occur. Reduced damage is correlated with an increase in long term survival.